A new high-efficiency optical-microwave mixing approach

High sensitivity reception is a crucial problem of fiber radio links. A significant improvement is obtained by applying a new approach called optical-microwave double mixing. The new approach can provide as much as 30 dB of higher mixing product in a narrow-band compared with the direct detection applying only additional passive components. Detailed investigation of the optical-microwave double-mixing method is shown to get optimum adjustment for specific applications. The new method is advantageously used for the reception of subcarrier-multiplexed optical signals.     

Probleme der Querkraftbiegung des geraden Stabs

Zusammenfassung Aus den Verformungsbedingungen für einen dünnwandigen Stabquerschnitt lassen sich beim zweidimensionalen Spannungszustand die Verw?lbung des Querschnitts durch die Querkraft und daraus dann die von der Querkraft hervorgerufenen Normalspannungen ermitteln. Man kann auch die Verschiebung der Stabachse durch die Querkraft auf diese Weise berechnen und die jetzt übliche, von A. Ritter stammende N?herungsformel durch einen genauen Ausdruck ersetzen. Das Verfahren wird an zwei Beispielen, dem Rechteckquerschnitt und dem Kreisringquerschnitt, n?her erl?utert.     

Morphology Analysis of the Scale Formed on Crofer 22APU Steel in Atmospheres Containing SO2

This work presents the results of a morphology analysis of the scale formed on Crofer 22APU steel at high temperature in atmospheres containing SO₂. The studies of steel oxidation were conducted on pre-oxidised and non-pre-oxidised steel within the temperature range of 700?C900 °C in a mixture of air of a varying SO₂ content and in pure air. In the case of oxidation in pure air it was established that on the surface of the Crofer 22APU a two-layer scale is formed. The outer layer of the scale contains MnCr₂O₄, whereas the inner layer contains Cr₂O₃. The scale formed in the atmosphere containing SO₂ is also comprised of two layers (outer MnCr₂O₄ and inner Cr₂O₃). The analyses were carried out with the use of the ³⁵S isotope. The analyses of the phase composition and morphology of the formed scale were conducted with the use of SEM/EDX and TEM.     

Proportioning with second-order information for model predictive control

We propose an algorithm for the effective solution of quadratic programming (QP) problems arising from model predictive control (MPC). MPC is a modern multivariable control method which gives the solution for a QP problem at each sample instant. Our algorithm combines the active-set strategy with the proportioning test to decide when to leave the actual active set. For the minimization in the face, we use a direct solver implemented by the Cholesky factors updates. The performance of the algorithm is illustrated by numerical experiments, and the results are compared with the state-of-the-art solvers on benchmarks from MPC.     

Oxidation Kinetics of Crofer 22APU Steel in an Atmosphere Containing SO2

The work presents an analysis of the oxidation rate of Crofer 22APU steel intended for the construction of inter-connectors in solid oxide fuel cells. Tests were conducted on two different samples of Crofer 22APU steel: pre-oxidized and unoxidized ones. Kinetic studies were carried out within the temperature range of fuel cells operation (873–1,173?K) in atmospheres with a varying nSO₂ content in the air (where n?=?0.1%, 1%, and 10%), as well as in pure air.     

Isogeometric thickness stretchable shell: Efficient formulation for nonlinear dynamic problems

An isogeometric shell element with through-thickness stretch is introduced and applied to quasi-static and dynamic problems. The shell element supports full three-dimensional constitutive laws, ie, the plane stress assumption is not required. An updated Lagrangian rate formulation is adopted, and biquadratic spline-based interpolation functions are used for in-plane interpolation. The concept of fiber mass scaling is proposed to lower the highest eigenfrequencies to improve the performance of the formulation. Clamped and unclamped knot vectors are compared, and the advantages of using unclamped knot vectors are demonstrated. The shell element is validated using several benchmark tests, which indicate good performance of the proposed formulation.     

Association of lumbar artery narrowing, degenerative changes in disc and endplate and apparent diffusion in disc on postcontrast enhancement of lumbar intervertebral disc

Objective  A decreased supply of nutrition to the intervertebral disc can lead to disc degeneration. Nutrient supply can be simulated in vivo by measuring gadolinium enhancement of the disc. We aimed to study the changes associated with disc degeneration that may have effect on the nutrition of the disc, i.e. lumbar artery narrowing, Modic changes, endplate defects, and apparent diffusion coefficient (ADC) in nucleus pulposus. Patients and methods  Twenty male volunteers underwent a lumbar spine examination at 1.5 T for anatomical imaging, diffusion weighted imaging, magnetic resonance angiography, and for T1 relaxation time quantification of contrast enhancement of intervertebral disc. Results  Enhancement of the disc increased with degeneration. Disc space narrowing associated strongly with the enhancement (Pearson’s correlation coefficient 0.46, P < 0.001). The enhancement rate in discs adjacent to Modic type 2 changes was 24%, adjacent to type 1/2 changes 58%, and 13% in the absence of Modic changes. Discs adjacent to endplate defects enhanced 32% compared to 10% of normal endplates. Lumbar artery narrowing or ADC in the disc were not associated with the enhancement. Conclusion  Increased enhancement of a degenerated disc is associated mostly with disc space narrowing and with the presence of degenerative endplate changes and endplate defects.     

NiPt sinter as a promising electrode for methanol electrocatalytic oxidation

Methanol is one of the chemical compounds utilized in fuel cells. The direct methanol fuel cell (DMFC) can be applied in many devices such as light electric vehicles and field equipment. Such a fuel cell is characterized by its high fuel energy density and low pollution. Despite many advantages of DMFCs, they are not commercially available, as the most efficient catalyst, which can be used in this process, has not been developed yet. Traditionally, it was platinum that was used in these fuel cells which is expensive and susceptible to CO poisoning. The solution to this is the use of bimetallic catalysts such as a NiPt system. In this study, we used a sintered NiPt electrode as the anode for the electrocatalytic oxidation of methanol. Based on our results, the sintered NiPt electrodes exhibited much higher activity in the oxidation of methanol, when compared with some conventional anodes.